There are three kinds of beis hapras: the first is a field in which a grave was plowed; this may be planted with any kind of tree but not with any kind of seed, only a seed that yields produce that can be reaped. If the produce is plucked, Rabbi Meir says that the threshing-floor must be piled up in the field and the produce must be sifted using two sieves. The Sages say that the grain must be sifted using two sieves but the pulse must be sifted using three sieves. Also, one must burn the straw and the stubble. This kind of beis hapras conveys ritual impurity through contact and by carrying but it doesn’t convey impurity by overshadowing.
The second kind of beis hapras is a field in which a grave has been lost. Such a field may be planted with any kind of seed but not be with any kind of tree. Trees may not be permitted to remain there except for shade trees that don’t produce fruit. Such a field conveys ritual impurity through contact, by carrying and by overshadowing.